This invention relates to a liquid dispensing, vapor controlling system and more particularly, to an improved, hybrid liquid dispensing, vapor recovery system and vapor collecting apparatus.
Hydrocarbon burning vehicles, e.g., automobiles, typically have their fuel tanks intermittently filled from stationary storage tanks from which liquid hydrocarbon fuel, e.g., gasoline, is dispensed through fuel dispensing nozzles during filling, or fuel dispensing operations. In the past, hydrocarbon vapors displaced from the fuel tank by the entering liquid fuel have been allowed to escape out the fuel tank inlet or fillpipe. However, various governmental regulations have been promulgated to require that the escaping vapor be controlled, and the State of California, California Air Resources Board, requires that liquid hydrocarbon fuel dispensing, vapor controlling systems be certified before being installed in that state. Currently available are several systems classifiable in three categories: secondary, vapor balance and hybrid. Secondary systems include those systems which employ a vacuum pump in a vapor control line to create a suction at the vehicle fillpipe/dispensing nozzle interface. Vapor balance systems include those which rely upon the pressure difference developed between the vapor space of the vehicle fuel tank and the vapor space of the storage tank as fuel is dispensed to the fuel tank. Hybrid systems include those which combine features of the secondary and vapor balance systems.
While the vapor recovery systems now certified for use in California have been somewhat useful, certain advantages remain unattained thereby. For example, a certified secondary system creates such an intense vacuum at the fillpipe/nozzle interface that large quantities of air are ingested from the environment into the vapor control line. As a result, the mixture of vapor and air could come within or near the explosive mixture limits of the fuel, thereby creating a risk of explosion. Also, a great proportion of the mixture of vapor and air must be incinerated, because the mixture cannot be returned to the storage tank without excessive pressurization thereof. The system with its incinerator is costly to produce, requires periodic maintenance by a skilled technician and tends toward high maintenance and operation costs.
As for the only hybrid system known to be certified, that system diverts about twenty percent of the fuel being dispensed away from the dispensing nozzle through an aspirator which pulls the vapor from the fuel tank. The diverted fuel and the vapor pass through a return line into the vapor space of the storage tank. Because twenty percent of the fuel is diverted, a significant increase in power consumption results. Also, because the system recirculates fuel to the vapor space of the storage tank, it encourages vapor growth therein.
Finally, a vapor balance system may require the maintenance of a tight seal at the fillpipe/nozzle interface.